linux-ext4 - [PATCH 08/39] tune2fs: don't change metadata

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Date:	Sat, 25 Oct 2014 13:57:15 -0700
From:	"Darrick J. Wong" <darrick.wong@...cle.com>
To:	tytso@....edu, darrick.wong@...cle.com
Cc:	linux-ext4@...r.kernel.org
Subject: [PATCH 08/39] tune2fs: don't change metadata_csum on a mounted fs

Don't let users change metadata_csum on a mounted filesystem because
there's no way to tell the kernel to turn on the feature; there's no
way to prevent the kernel from rewriting on-disk structures while
tune2fs is also rewriting them; and there's no way to tell the kernel
to reload them after tune2fs is finished.

Signed-off-by: Darrick J. Wong <darrick.wong@...cle.com>
---
 misc/tune2fs.c |    6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/misc/tune2fs.c b/misc/tune2fs.c
index ecbdea0..7fee870 100644
--- a/misc/tune2fs.c
+++ b/misc/tune2fs.c
@@ -1110,6 +1110,9 @@ mmp_error:
 		       EXT4_FEATURE_RO_COMPAT_METADATA_CSUM)) {
 		if (check_fsck_needed(fs))
 			exit(1);
+		if (mount_flags & EXT2_MF_MOUNTED)
+			fputs(_("Cannot enable metadata_csum on a mounted "
+				"filesystem!\n"), stderr);
 		rewrite_checksums = 1;
 		/* metadata_csum supersedes uninit_bg */
 		fs->super->s_feature_ro_compat &=
@@ -1132,6 +1135,9 @@ mmp_error:
 			EXT4_FEATURE_RO_COMPAT_METADATA_CSUM)) {
 		if (check_fsck_needed(fs))
 			exit(1);
+		if (mount_flags & EXT2_MF_MOUNTED)
+			fputs(_("Cannot disable metadata_csum on a mounted "
+				"filesystem!\n"), stderr);
 		rewrite_checksums = 1;
 		/*
 		 * If we're turning off metadata_csum and not turning on

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